XI2 provides a number of features over the current X Input Extension 1.5:

Explicit support for the master/slave device hierarchy. In X servers supporting XI2 there are two general types of devices - master devices and slave devices. Slave devices (SDs) usually represent a physical input device connected to the host computer. Master devices (MDs) are virtual input devices that are controlled by the physical input devices. Master devices appear as master pointers (i.e. a visible cursor) and master keyboards (i.e. a keyboard focus). Each time an SD generates an event, this event is passed through the MD to the respective application.

Support for multiple master devices. XI2 provides applications with the ability to create additional pairs of master devices (i.e one cursor and one keyboard focus). Through dynamic reattachment of SDs applications can control which physical device controls which visible cursor/keyboard focus. This allows multiple co-located users to collaborate on a single screen.

Support for 32 bit keycodes. Many multimedia keys cannot be processed in current X servers as the core protocol limits keycodes to a maximum of 255. Applications built against XI2 may receive keycodes up to 32 bit.

Verify that the cursors work independently. If both master devices are used in two different applications, they should work independently and simultaneously. If both devices are used in the same application, some restrictions apply.

Remove the master device again with 'xinput --remove-master "<name> pointer"'

The above is the test plan to verify multiple input devices work with legacy applications. To develop new XI2-capable applications, please see the XI2 man pages and the example programs below in #Documentation.

XI2 has no effect on the traditional desktop interface. Only applications that make use of the new APIs gain benefits.
Users who explicitly create additional master devices (e.g. using the xinput tool) may be able to use their traditional desktop in a multi-user fashion to a limited extent.

The update to X.Org server 1.7 provides Fedora with the X Input Extension version 2.0 (XI2). This extension provides a new client API for handling input devices and also Multi-Pointer X (MPX) functionality. MPX functionality allows users to create and remove new cursors and keyboard foci on the fly and dynamically reattach physical input devices to these cursors/foci. Each cursor/foci pair is independent of the others and can be used simultaneously, allowing for multi-user interaction on a single screen, bi-manual input and more.
The XI2 API provides clients with full access to each input device and its events. Clients can thus treat events from each input devices separately, implementing features such as multi-user editing in the same document.